Additive building material mixtures containing solid microparticles

ABSTRACT

The present invention relates to the use of compact polymeric microparticles in hydraulically setting building material mixtures for the purpose of enhancing their frost resistance and cyclical freeze/thaw durability.

The present invention relates to the use of polymeric microparticles inhydraulically setting building material mixtures for the purpose ofenhancing their frost resistance and cyclical freeze/thaw durability.

Concrete is an important building material and is defined by DIN 1045(07/1988) as artificial stone formed by hardening from a mixture ofcement, aggregate and water, together where appropriate with concreteadmixtures and concrete additions. One way in which concrete isclassified is by its subdivision into strength groups (BI-BII) andstrength classes (B5-B55). Adding gas-formers or foam-formers to the mixproduces aerated concrete or foamed concrete (Römpp Lexikon, 10th ed.,1996, Georg Thieme Verlag).

Concrete has two time-dependent properties. Firstly, by drying out, itundergoes a reduction in volume that is termed shrinkage. The majorityof the water, however, is bound in the form of water of crystallization.Concrete, rather than drying, sets: that is, the initially highly mobilecement paste (cement and water) starts to stiffen, becomes rigid, and,finally, solidifies, depending on the timepoint and progress of thechemical/mineralogical reaction between the cement and the water, knownas hydration. As a result of the water-binding capacity of the cement itis possible for concrete, unlike quicklime, to harden and remain solideven under water. Secondly, concrete undergoes deformation under load,known as creep.

The freeze/thaw cycle refers to the climatic alternation of temperaturesaround the freezing point of water. Particularly in the case ofmineral-bound building materials such as concrete, the freeze/thaw cycleis a mechanism of damage. These materials possess a porous, capillarystructure and are not watertight. If a structure of this kind that isfull of water is exposed to temperatures below 0° C., then the waterfreezes in the pores. As a result of the density anomaly of water, theice then expands. This results in damage to the building material.Within the very fine pores, as a result of surface effects, there is areduction in the freezing point. In micropores water does not freezeuntil below −17° C. Since, as a result of freeze/thaw cycling, thematerial itself also expands and contracts, there is additionally acapillary pump effect, which further increases the absorption of waterand hence, indirectly, the damage. The number of freeze/thaw cycles istherefore critical with regard to damage.

Decisive factors affecting the resistance of concrete to frost and tocyclical freeze/thaw under simultaneous exposure to thawing agents; arethe imperviousness of its microstructure, a certain strength of thematrix, and the presence of a certain pore microstructure. Themicrostructure of a cement-bound concrete is traversed by capillarypores (radius: 2 μm-2 mm) and gel pores (radius: 2-50 nm). Water presentin these pores differs in its state as a function of the pore diameter.Whereas water in the capillary pores retains its usual properties, thatin the gel pores is classified as condensed water (mesopores: 50 nm) andadsorptively bound surface water (micropores: 2 nm), the freezing pointsof which may for example be well below −50° C. [M. J. Setzer,Interaction of water with hardened cement paste, Ceramic Transactions 16(1991) 415-39]. Consequently, even when the concrete is cooled to lowtemperatures, some of the water in the pores remains unfrozen(metastable water). For a given temperature, however, the vapor pressureover ice is lower than that over water. Since ice and metastable waterare present alongside one another simultaneously, a vapor-pressuregradient develops which leads to diffusion of the still-liquid water tothe ice and to the formation of ice from said water, resulting inremoval of water from the smaller pores or accumulation of ice in thelarger pores. This redistribution of water as a result of cooling takesplace in every porous system and is critically dependent on the type ofpore distribution.

The artificial introduction of microfine air pores in the concrete hencegives rise primarily to what are called expansion spaces for expandingice and ice-water. Within these pores, freezing water can expand orinternal pressure and stresses of ice and ice-water can be absorbedwithout formation of microcracks and hence without frost damage to theconcrete. The fundamental way in which such air-pore systems act hasbeen described, in connection with the mechanism of frost damage toconcrete, in a large number of reviews [Schulson, Erland M. (1998) Icedamage to concrete. CRREL Special Report 98-6; S. Chatterji, Freezing ofair-entrained cement-based materials and specific actions ofair-entraining agents, Cement & Concrete Composites 25 (2003) 759-65; G.W. Scherer, J. Chen & J. Valenza, Methods for protecting concrete fromfreeze damage, U.S. Pat. No. 6,485,560 B1 (2002); M. Pigeon, B. Zuber &J. Marchand, Freeze/thaw resistance, Advanced Concrete Technology 2(2003) 11/1-11/17; B. Erlin & B. Mather, A new process by which cyclicfreezing can damage concrete—the Erlin/Mather effect, Cement & ConcreteResearch 35 (2005) 1407-11].

A precondition for improved resistance of the concrete on exposure tothe freezing and thawing cycle is that the distance of each point in thehardened cement from the next artificial air pore does not exceed adefined value. This distance is also referred to as the “Powers spacingfactor” [T. C. Powers, The air requirement of frost-resistant concrete,Proceedings of the Highway Research Board 29 (1949) 184-202]. Laboratorytests have shown that exceeding the critical “Power spacing factor” of500 μm leads to damage to the concrete in the freezing and thawingcycle. In order to achieve this with a limited air-pore content, thediameter of the artificially introduced air pores must therefore be lessthan 200-300 μm [K. Snyder, K. Natesaiyer & K. Hover, The stereologicaland statistical properties of entrained air voids in concrete: Amathematical basis for air void systems characterization, MaterialsScience of Concrete VI (2001) 129-214].

The formation of an artificial air-pore system depends critically on thecomposition and the conformity of the aggregates, the type and amount ofthe cement, the consistency of the concrete, the mixer used, the mixingtime, and the temperature, but also on the nature and amount of theagent that forms the air pores, the air entrainer. Although theseinfluencing factors can be controlled if account is taken of appropriateproduction rules, there may nevertheless be a multiplicity of unwantedadverse effects, resulting ultimately in the concrete's air contentbeing above or below the desired level and hence adversely affecting thestrength or the frost resistance of the concrete.

Artificial air pores of this kind cannot be metered directly; instead,the air entrained by mixing is stabilized by the addition of theaforementioned air entrainers [L. Du & K. J. Folliard, Mechanism of airentrainment in concrete, Cement & Concrete Research 35 (2005) 1463-71].Conventional air entrainers are mostly surfactant-like in structure andbreak up the air introduced by mixing into small air bubbles having adiameter as far as possible of less than 300 μm, and stabilize them inthe wet concrete microstructure. A distinction is made here between twotypes.

One type—for example sodium oleate, the sodium salt of abietic acid orVinsol resin, an extract from pine roots—reacts with the calciumhydroxide of the pore solution in the cement paste and is precipitatedas insoluble calcium salt. These hydrophobic salts reduce the surfacetension of the water and collect at the interface between cementparticle, air and water. They stabilize the microbubbles and aretherefore encountered at the surfaces of these air pores in the concreteas it hardens. The other type—for example sodium lauryl sulfate (SDS) orsodium dodecylphenylsulfonate—reacts with calcium hydroxide to formcalcium salts which, in contrast, are soluble, but which exhibit anabnormal solution behavior. Below a certain critical temperature thesolubility of these surfactants is very low, while above thistemperature their solubility is very good. As a result of preferentialaccumulation at the air/water boundary they likewise reduce the surfacetension, thus stabilize the microbubbles, and are preferably encounteredat the surfaces of these air pores in the hardened concrete.

The use of these prior-art air entrainers is accompanied by a host ofproblems [L. Du & K. J. Folliard, Mechanism of air entrainment inconcrete, Cement & Concrete Research 35 (2005) 1463-71]. For example,prolonged mixing times, different mixer speeds and altered meteringsequences in the case of ready-mix concretes result in the expulsion ofthe stabilized air (in the air pores).

The transporting of concretes with extended transport times, poortemperature control and different pumping and conveying equipment, andalso the introduction of these concretes in conjunction with alteredsubsequent processing, jerking and temperature conditions, can produce asignificant change in an air-pore content set beforehand. In the worstcase this may mean that a concrete no longer complies with the requiredlimiting values of a certain exposure class and has therefore becomeunusable [EN 206-1 (2000), Concrete—Part 1: Specification, performance,production and conformity].

The amount of fine substances in the concrete (e.g. cement withdifferent alkali content, additions such as flyash, silica dust or coloradditions) likewise adversely affects air entrainment. There may also beinteractions with flow improvers that have a defoaming action, and henceexpel air pores, but may also introduce them in an uncontrolled manner.

A relatively new possibility for improving the frost resistance andcyclical freeze/thaw durability is to achieve the air content by theadmixing or solid metering of polymeric microparticles (hollowmicrospheres) [H. Sommer, A new method of making concrete resistant tofrost and de-icing salts, Betonwerk & Fertigteiltechnik 9 (1978)476-84]. Since the microparticles generally have particle sizes of lessthan 100 μm, they can also be distributed more finely and uniformly inthe concrete microstructure than can artificially introduced air pores.Consequently, even small amounts are sufficient for sufficientresistance of the concrete to the freezing and thawing cycle. The use ofpolymeric microparticles of this kind for improving the frost resistanceand cyclical freeze/thaw durability of concrete is already known fromthe prior art [cf. DE 2229094 A1, U.S. Pat. No. 4,057,526 B1, U.S. Pat.No. 4,082,562 B1, DE 3026719 A1]. The microparticles described thereinare notable in particular for the fact that they possess a void smallerthan 200 μm (in diameter) and that this hollow core consists of air (ora gaseous substance). This likewise includes porous microparticles fromthe 100 μm scale, which may possess a multiple of relatively small voidsand/or pores.

Compact polymeric microparticles have not been considered to date inpractice for the purpose of enhancing the frost resistance and cyclicalfreeze/thaw durability.

For the hollow microspheres, however, relatively high levels of additionare needed in order to obtain values below the critical “Power spacingfactor”, the reason for this lying at least partly in the large particlediameter of >100 μm. This fact, in combination with the high preparationcosts, a result of the multistage preparation processes, have beendetrimental to the establishment of these technologies on the market.

The object on which the present invention is based, therefore, was toprovide a means of improving the frost resistance and cyclicalfreeze/thaw durability for hydraulically setting building materialmixtures that develops its full activity even at relatively low levelsof addition, and which, moreover, can be prepared easily andinexpensively. A further object was not, or not substantially, to impairthe mechanical strength of the building material mixture as a result ofsaid means.

It has now been found, surprisingly, that compact polymericmicroparticles of single-stage or multistage synthesis are also suitablefor improvements to the frost resistance and/or cyclical freeze/thawdurability for hydraulically setting building material mixtures. Bymicroparticles of single-stage synthesis are meant a particle (without ashell) which is synthesized homogeneously in the composition. This isall the more surprising since these polymeric microparticles do notentrain any air into the construction mixture.

The mode of action can be explained as follows: the polymericmicroparticles of the invention are in homogeneous distribution in theconstruction mixture. A cavity between microparticle and curedconstruction mixture, which possibly becomes further enlarged as aresult of the contraction of the construction mixture on curing, servesas an expansion site for freezing water. The uniform distribution ofthese capillary-active pores, with an average spacing from one anotherwhich is smaller than the “Power spacing factor”, then provides for theincrease in frost resistance and/or cyclical freeze/thaw durability.

Through the use of the polymeric formations of the invention it ispossible to keep the introduction of air into the building materialmixture at an extraordinarily low level. As a result, markedly improvedcompressive strengths are achievable in the concrete. Consequently it ispossible to achieve strength classes which can be set otherwise only bymeans of a substantially lower water/cement value (w/c value). Low w/cvalues, however, in turn considerably restrict the processability of theconcrete in certain circumstances. Higher compressive strengths are ofinterest, in addition and in particular, insofar as it is possible toreduce the cement content of the concrete, which is needed for strengthto develop, as a result of which it is possible to achieve a significantlowering in the price per m³ of concrete.

The polymeric microparticles comprise at least one monoethylenicallyunsaturated monomer. The microparticles may be single-stage ormultistage, and the comonomer composition of the individual stages maybe different. Preferably included are, among others, nitriles of(meth)acrylic acid, and other nitrogen-containing methacrylates, such asmethacryloylamidoacetonitrile, 2-methacryloyloxyethylmethylcyanamide,cyanomethyl methacrylate; carbonyl-containing methacrylates, such asoxazolidinylethyl methacrylate, N-(methacryloyloxy)formamide, acetonylmethacrylate, N-methacryloyl-morpholine, N-methacryloyl-2-pyrrolidonone;glycol dimethacrylates, such as 1,4-butanediol methacrylate,2-butoxyethyl methacrylate, 2-ethoxyethoxymethyl methacrylate,2-ethoxyethyl methacrylate, methacrylates of ether alcohols, such astetrahydrofurfuryl methacrylate, vinyloxyethoxyethyl methacrylate,methoxy-ethoxyethyl methacrylate, 1-butoxypropyl methacrylate,1-methyl-(2-vinyloxy)-ethyl methacrylate, cyclohexyloxymethylmethacrylate, methoxymethoxyethyl methacrylate, benzyloxymethylmethacrylate, furfuryl methacrylate, 2-butoxy-ethyl methacrylate,2-ethoxyethoxymethyl methacrylate, 2-ethoxyethyl methacrylate,allyloxymethyl methacrylate, 1-ethoxybutyl methacrylate, methoxymethylmethacrylate, 1-ethoxyethyl methacrylate, ethoxymethyl methacrylate;oxiranyl methacrylates, such as 2,3-epoxybutyl methacrylate,3,4-epoxybutyl methacrylate, glycidyl methacrylate; phosphorus-,boron-and/or silicon-containing methacrylates, such as2-(dimethylphosphato)propyl methacrylate, 2-(ethylenephosphito)propylmethacrylate, dimethylphosphino-methyl methacrylate,dimethylphosphonoethyl methacrylate, diethyl methacryloylphosphonate,dipropyl methacryloyl phosphate; sulfur-containing methacrylates, suchas ethylsulfinylethyl methacrylate, 4-thiocyanatobutyl methacrylate,ethylsulfonylethyl methacrylate, thiocyanatomethyl methacrylate,methylsulfinylmethyl methacrylate, and bis(methacryloyloxyethyl)sulfide; vinyl esters, such as vinyl acetate;

styrene, substituted styrenes with an alkyl substituent in the sidechain, such as *methylstyrene and *ethylstyrene, for example,substituted styrenes with an alkyl substituent on the ring, such asvinyl toluene and p-methylstyrene;

heterocyclic vinyl compounds, such as 2-vinylpyridine, 3-vinylpyridine,2-methyl-5-vinylpyridine, 3-ethyl-4-vinylpyridine,2,3-dimethyl-5-vinylpyridine, vinylpyrimidine, vinylpiperidine,9-vinylcarbazole, 3-vinylcarbazole, 4-vinylcarbazole, 1-vinylimidazole,2-methyl-1-vinylimidazole, N-vinyl-pyrrolidone, 2-vinylpyrrolidone,N-vinylpyrrolidine, 3-vinylpyrrolidine, N-vinyl-caprolactam,N-vinylbutyrolactam, vinyloxolane, vinylfuran, vinylthiophene,vinylthiolane, vinylthiazoles and hydrogenated vinylthiazoles,vinyloxazoles and hydrogenated vinyloxazoles;

vinyl and isoprenyl ethers;

maleic acid derivatives, such as diesters of maleic acid, the alcoholresidues having 1 to 9 carbon atoms, maleic anhydride, methylmaleicanhydride, maleimide, and methylmaleimide;

fumaric acid derivatives, such as diesters of fumaric acid, the alcoholresidues having 1 to 9 carbon atoms;

α-olefins such as ethene, propene, n-butene, isobutene, n-pentene,isopentene, n-hexene, isohexene; cyclohexene.

In addition it has been found that by means of corresponding monomers itis possible to bring about, in addition to the ionic repulsion, thesteric repulsion of the polymeric formations as well. This leads to anadditional stabilization of the polymeric formations in the dispersionand the construction mixture.

In accordance with the invention it is therefore also possible to usefree-radically polymerizable monomers having a molar mass of greaterthan 200 g/mol which carry a hydrophilic radical. Particular preferenceis given to monomers which carry a polyethylene oxide block having twoor more units of ethylene oxide. Preference is given to using monomersfrom the group of (meth)acrylic esters of methoxypoiyethyiene glycolCH₃O(CH₂CH₂O)_(n)H, (with n=2), (meth)acrylic esters of an ethoxylatedC16-C18 fatty alcohol mixture (with 2 or more ethylene oxide units),methacrylic esters of 5-tert-octylphenoxypolyethoxyethanol (with 2 ormore ethylene oxide units), nonylphenoxypolyethoxyethanol (with 2 ormore ethylene oxide units) or mixtures thereof.

In addition there may be one or more monoethylenically unsaturatedmonomers containing an acid group present. Preference is given toacrylic acid, methacrylic acid, ethacrylic acid, a-chloroacrylic acid,a-cyanoacrylic acid, p-methylacrylic acid (crotonic acid),a-phenylacrylic acid, p-acryloyloxypropionic acid, sorbic acid,a-chlorosorbic acid, 2′-methylisocrotonic acid, cinnamic acid,p-chlorocinnamic acid, p-stearylic acid, itaconic acid, citraconic acid,mesacronic acid, glutaconic acid, aconitic acid, maleic acid, fumaricacid, tricarboxyethylene, and maleic anhydride, hydroxyl-oramino-containing esters of the above acids, preferably of acrylic ormethacrylic acid, such as 2-hydroxyethyl acrylate,N,N-dimethylaminoethyl acrylate, and the analogous derivatives ofmethacrylic acid, particular preference being given to acrylic acid andalso methacrylic acid and preference beyond that to acrylic acid.

In addition to the monoethylenically unsaturated monomer containing anacid group, this polymer may also be based on further comonomers otherthan the monoethylenically unsaturated monomer containing an acid group.Preferred comonomers are ethylenically unsaturated sulfonic acidmonomers, ethylenically unsaturated phosphonic acid monomers, andacrylamides, preferably.

Ethylenically unsaturated sulfonic acid monomers are preferablyaliphatic or aromatic vinylsulfonic acids or acrylic or methacrylicsulfonic acids. Preferred aliphatic or aromatic vinylsulfonic acids arevinylsulfonic acid, allylsulfonic acid, 4-vinylbenzylsulfonic acid,vinyltoluenesulfonic acid, and styrenesulfonic acid. Preferredacryloyl-and methacryloylsulfonic acids are sulfoethyl acrylate,sulfoethyl methacrylate, sulfopropyl acrylate, sulfopropyl methacrylate,2-hydroxy-3-methacryloyloxypropylsulfonic acid, and2-acrylamido-2-methyl-propanesulfonic acid.

Ethylenically unsaturated phosphonic acid monomers such asvinylphosphonic acid, allylphosphonic acid, vinylbenzylphosphonic acid,acrylamidoalkylphosphonic acids, acrylamidoalkyldiphosphonic acids.Phosphonomethylated vinylamines, (meth)acryloylphosphonic acidderivatives.

Possible acrylamides are alkyl-substituted acrylamides oraminoalkyl-substituted derivatives of acrylamide or of methacrylamide,such as N-vinyl-amides, N-vinylformamides, N-vinylacetamides,N-vinyl-N-methylacetamides, N-vinyl-N-methylformamides,N-methylol(meth)acrylamide, vinylpyrrolidone,N,N-dimethylpropylacrylamide, dimethylacrylamide or diethylacrylamide,and the corresponding methacrylamide derivatives, and also acrylamideand methacrylamide, preference being given to acrylamide.

The chemical crosslinking can be achieved by crosslinkers generallyknown to the skilled worker. The crosslinkers may be present in anystate. Inventively preferred crosslinkers are polyacrylic orpolymethacrylic esters, which are obtained, for example, through thereaction of a polyol or ethoxylated polyol such as ethylene glycol,propylene glycol, trimethylolpropane, 1,6-hexanediol-glycerol,pentaerythritol, polyethylene glycol or polypropylene glycol withacrylic acid or methacrylic acid. Use may also be made of polyols, aminoalcohols and also their mono(meth)acrylic esters, and monoallyl ethers.Additionally also acrylic esters of monoallyl compounds of the polyolsand amino alcohols. Another group of crosslinkers is obtained throughthe reaction of polyalkylenepolyamines such as diethylenetriamine andtriethylenetetra-aminemethacrylic acid or methacrylic acid. Suitablecrosslinkers include 1,4-butanediol diacrylate, 1,4-butanedioldimethacrylate, 1,3-butylene glycol diacrylate, 1,3-butylene glycoldimethacrylate, diethylene glycol diacrylate, diethylene glycoldimethacrylate, ethoxylated bisphenol A diacrylate, ethoxylatedbisphenol A dimethacrylate, ethylene glycol dimethacrylate,1,6-hexanedioi diacrylate, 1,6-hexanediol dimethacrylate, neopentylglycol dimethacrylate, polyethylene glycol diacrylate, polyethyleneglycol dimethacrylate, triethylene glycol diacrylate, triethylene glycoldimethacrylate, tripropylene glycol diacrylate, tetraethylene glycoldiacrylate, tetraethylene glycol diacrylate, tetraethylene glycoldimethacrylate, dipentaerythritol pentaacrylate, pentaerythritoltetraacrylate, pentaerythritol triacrylate, trimethylolpropanetriacrylate, trimethylol trimethacrylate,tris(2-hydroxyethyl)isocyanoratetriacrylate, tris(2-hydroxy)isocyanoratetrimethacrylate, divinyl esters of polycarboxylic acids, diallyl estersof polycarboxylic acids, triallyl terephthalate, diallyl maleate,diallyl fumarate, hexamethylenebismaleimide, trivinyl trimellitate,divinyl adipate, diallyl succinate, and ethylene glycol divinyl ether,cyclopentadiene diacrylate, triallylamine, tetraallylammonium halides,divinylbenzene, divinyl ether, N,N′-methylenebisacrylamide,N,N′-methylene-bismethacrylamide, ethylene glycol dimethacrylate, andtrimethylolpropane triacrylate. Crosslinkers preferred among these areN,N′-methylene-bisacrylamide, N,N′-methylenebismethacrylamide,polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, andtriallylamine.

The polymeric formations of the invention can be prepared preferably byemulsion polymerization and preferably have an average particle size of10 to 5000 nm; an average particle size of 150 to 2000 nm isparticularly preferred. Most preferable are average particle sizes of200 to 1000 nm.

The average particle size is determined, for example, by counting astatistically significant amount of particles by means of transmissionelectron micrographs.

For the preparation of the polymeric formations of the invention it ispossible to employ all of the initiators and regulators that arecustomary for emulsion polymerization. Examples of initiators areinorganic peroxides, organic peroxides or H₂O₂, and also mixturesthereof with, if appropriate, one or more reducing agents.

In accordance with the invention it is possible to employ any ionic ornonionic emulsifier during or after the preparation of the dispersion.

Whereas the water-filled polymeric microparticles are used in accordancewith the invention preferably in the form of an aqueous dispersion, itis entirely possible within the context of the present invention to addthe water-filled microparticles directly as a solid to the buildingmaterial mixture. For that purpose the microparticles are for examplecoagulated—by methods known to the skilled worker—and isolated from theaqueous dispersion by means of standard methods (e.g. filtration,centrifuging, sedimentation and decanting). The material obtained can bewashed and is subsequently dried.

The polymeric formations are added to the building material mixture in apreferred amount of 0.01% to 5% by volume, in particular 0.1% to 0.5% byvolume. The building material mixture, in the form for example ofconcrete or mortar, may in this case include the customary hydraulicallysetting binders, such as cement, lime, gypsum or anhydrite, for example.

1. A hydraulically setting building material mixture, consistingessentially of: a hydraulically setting building material: and polymericmicroparticles which are synthesized in one or more stages from at leastone ethylenically unsaturated monomer; wherein said polymericmicroparticles are in the form of spray-dried, coagulated orfreeze-dried powder: and wherein said ethylenically unsaturated monomeris selected from the group consisting of nitriles of (meth)acrylic acid,nitrogen-containing methacrylates, carbonyl-containing methacrylates,glycol dimethacrylates, methacrylates of ether alcohols, oxiranylmethacrylates, phosphorus-containing methacrylates, boron-containingmethacrylates, silicon-containing methacrylates, sulfur-containingmethacrylates, vinyl esters, styrene, substituted styrenes with an alkylsubstituent in the side chain, heterocyclic vinyl compounds, vinylethers, isoprenyl ethers, maleic acid compounds, fumaric acid compounds,α-olefins and mixtures thereof.
 2. The hydraulically setting buildingmaterial mixture according to claim 1, wherein the ethylenicallyunsaturated monomer is selected from the group consisting of styrene,butadiene, vinyltoluene, ethylene, propylene, vinyl acetate, vinylchloride, vinylidene chloride, acrylonitrile, acrylamide,methacrylamide, C₁-C₁₈ alkyl esters of acrylic acid, C₁-C₁₈ alkyl estersof methacrylic acid, and mixtures thereof.
 3. The hydraulically settingbuilding material mixture according to claim 1, wherein said polymericmicroparticles further comprise at least one crosslinker.
 4. Thehydraulically setting building material mixture according to claim 3,wherein said crosslinker is selected from the group consisting ethyleneglycol di(meth)acrylate, propylene glycol di(meth)acrylate, allyl(meth)acrylate, divinylbenzene, diallylmaleate, trimethylolpropanetrimethacrylate, glycerol dimethacrylate, glycerol trimethacrylate,pentaerythritol tetramethacrylate, and mixtures thereof.
 5. Thehydraulically setting building material mixture according to claim 1,wherein the said polymeric microparticles are in the form of adispersion.
 6. The hydraulically setting building material mixtureaccording to claim 1 wherein said polymeric microparticles are in theform of spray-dried, coagulated or freeze-dried powder.
 7. Thehydraulically setting building material mixture according to claim 1,wherein the polymeric microparticles have an average particle size of 10to 5000 nm.
 8. The hydraulically setting building material mixtureaccording to claim 1, wherein the polymeric microparticles are used inan amount of 0.01% to 5% by volume, based on the volume of the buildingmaterial mixture.
 9. The hydraulically setting building material mixtureaccording to claim 1, wherein the polymeric microparticles are used inan amount of 0.1% to 0.5% by volume, based on the volume of the buildingmaterial mixture.
 10. The hydraulically setting building materialmixture according to claim 1, further comprising a binder selected fromthe group consisting of cement, lime, gypsum anhydrite and mixturesthereof.
 11. The hydraulically setting building material mixtureaccording to claim 1, which comprises concrete or mortar.
 12. A methodof producing a hydraulically setting building material mixture,comprising: adding polymeric microparticles to a setting buildingmaterial, wherein said polymeric microparticles are synthesized in oneor more stages from at least one ethylenically unsaturated monomer;wherein said polymeric microparticles are in the form of spray-dried,coagulated or freeze-dried powder, wherein said hydraulically settingbuilding material mixture consists essentially of said polymericmicroparticles and said setting building material; and wherein saidethylenically unsaturated monomer is selected from the group consistingof nitriles of (meth)acrylic acid, nitrogen-containing methacrylates,carbonyl-containing methacrylates, glycol dimethacrylates, methacrylatesof ether alcohols, oxiranyl methacrylates, phosphorus-containingmethacrylates, boron-containing methacrylates, silicon-containingmethacrylates, sulfur-containing methacrylates, vinyl esters, styrene,substituted styrenes with an alkyl substituent in the side chain,heterocyclic vinyl compounds, vinyl ethers, isoprenyl ethers, maleicacid compounds, fumaric acid compounds, α-olefins and mixtures thereof.13. The method according to claim 1, wherein the ethylenicallyunsaturated monomer is selected from the group consisting of styrene,butadiene, vinyltoluene, ethylene, propylene, vinyl acetate, vinylchloride, vinylidene chloride, acrylonitrile, acrylamide,methacrylamide, C₁-C₁₈ alkyl esters of acrylic acid, C₁-C₁₈ alkyl estersof methacrylic acid, and mixtures thereof.
 14. The method according toclaim 1, wherein said polymeric microparticles further comprise at leastone crosslinker.
 15. The method according to claim 14, wherein saidcrosslinker is selected from the group consisting of ethylene glycoldi(meth)acrylate, propylene glycol di (meth)acrylate, allyl(meth)acrylate, divinylbenzene, diallylmaleate, trimethylolpropanetrimethacrylate, glycerol dimethacrylate, glycerol trimethacrylate,pentaerythritol tetramethacrylate, and mixtures thereof.
 16. The methodaccording to claim 1, wherein said polymeric microparticles are in theform of a dispersion.
 17. The method according to claim 1, wherein saidpolymeric microparticles are in the form of spray-dried, coagulated orfreeze-dried powder.
 18. The method according to claim 1, wherein thepolymeric microparticles have an average particle size of 10 to 5000 nm.19. The method according to claim 1, wherein the polymericmicroparticles are used in an amount of 0.01% to 5% by volume, based onthe volume of the building material mixture.
 20. The method according toclaim 1, wherein the polymeric microparticles are used in an amount of0.1% to 0.5% by volume, based on the volume of the building materialmixture.
 21. The method according to claim 1, further comprising abinder selected from the group consisting of cement, lime, gypsumanhydrite and mixtures thereof.
 22. The method according to claim 1,which comprises concrete or mortar.
 23. A hydraulically setting buildingmaterial mixture, comprising: a hydraulically setting building material;and polymeric microparticles which are synthesized in one or more stagesfrom at least one ethylenically unsaturated monomer; wherein saidpolymeric microparticles are homogeneously distributed in said mixture;and wherein capillary-active pores have an average spacing from oneanother which is smaller than a power spacing factor.